Servo-assisted gear selector

ABSTRACT

Servo-assisted gear selection for a vehicle gearbox and gear change controlled by the driver by actuating the clutch, wherein the driver is informed of the selection having been performed in the gearbox by a haptic or tactile signal at the clutch pedal. The signal is transmitted mechanically from an electromagnet to the clutch pedal, or the electromagnet is arranged in the pedal plate of the clutch pedal. The signal generator may also consist of an electromagnet in conjunction with a pressure piston, which acts on the pressure line of the clutch actuating mechanism, or of an electropneumatic valve in conjunction with a differential piston signal generator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/EP88/00578 filed June 30,1988 based upon German National application P 37 24 272.5 of July 22,1987 under the International Convention.

FIELD OF THE INVENTION

The present invention relates to a servo-assisted gear selector forvehicle gearboxes with gear preselection and gear change controlled bythe driver by actuating the clutch at the clutch pedal and wherein thedriver is informed of the selection performed in the gearbox by asignal.

BACKGROUND OF THE INVENTION

Such gear selectors, in which the driver or an electronic device merelyselects the gear, and the gear change is performed in the gearbox properby a servo-assisted actuating device rather than directly by the drivervia a shifting linkage, have been known in many designs, e.g.,

ZF [Zahnradfabrik Friedrichshafen AG ] Specification forelectropneumatic selection (ES) for synchromesh transmissions F 43546/RT3430-885,

ZF specifications for automated preselector (APS) for synchromeshtransmissions F 32437/RT 3431-885.

electronic-pneumatic selector EPS for trucks of Daimler BenzAktiengesellschaft, Order No. 6510302300 of March 1986,

Scania - Leichter schalten mit Computer (Shift more easily by aComputer), page 4, column 2, paragraph 2.

In all these designs, the clutch and consequently the drive trainbetween the engine and the gearbox is disengaged and engaged, as before,by the driver via the clutch pedal by the driver. While in the case ofgear selection via a shifting linkage, the driver recognizes when thegear has been selected as a consequence of the direct contact with theshifting means in the gearbox, this information, which is generated inconjunction with the actuation of the gear shift lever and the shiftinglinkage, is lacking in the case of a servo-assisted gear selector. Toensure properly timed actuation of the clutch, especially for engagingthe clutch after completion of the selection in the gearbox, acorresponding feedback must be generated in order to again engage thedrive train disengaged via the clutch shortly after completion of theselection process in the gearbox.

It is known from the first-mentioned ZF publication for anelectropneumatic selector (ES) that the corresponding gear can beselected with the lever of the gear selector. A noticeable restoringforce acts against the selection movement, and this force is abolishedas soon as the gear selected in the gearbox is thrown in. The lever cannow be moved easily into the end position. This also represents a signalfor re-engagement for the driver.

In the automated preselector (APS) according to the second ZFpublication, the feedback on completion of the selection is an acousticfeedback generated by a buzzer, page 2, column 2, paragraph 1. This alsorepresents the signal for re-engagement for the driver. According to theEPS Manual on trucks of Daimler Benz Aktiengesellschaft, page 8, theselection is complete only when the gear shift lever can be movedfarther out of a looked preselected position into position 2, which ispresent in each direction of shifting. The clutch pedal and the gearshift lever can be released only when the gear selected is shown in thedisplay.

It is recognizable from the Scania brochure titled "Leichter Schaltenmit Computern" (Shift more easily by a Computer), page 4, paragraph 1,that a buzzing tone signals to the driver when the selection process iscomplete and the clutch can be released.

Even though the connection of the feedback for the selection performedin the gearbox to the gear shift lever does provide the driver withinformation, which comes closest to the information from a gear selectorwith a shifting linkage, it is bound, as is shown by the examplespresented, to the gear shift lever or a comparable gear shifting lever,and involves high cost of construction.

Even though an acoustic signal can be easily realized, it is notparticularly suitable as information for the driver, and such signalsare burdensome in the case of frequent gear shiftings. In addition,acoustic signals are used as warning signals, whereas the feedback onthe selection in a gearbox represents a perfectly normal, but necessarypiece of information in the case of servo-assisted selection.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide animproved feedback for the selection performed in the gearbox in aservo-assisted gear selector and, in particular, such that this feedbackis bound to a gear selector lever or gear shift lever, and will also notbe an acoustic signal.

SUMMARY OF THE INVENTION

This object is achieved, in accordance with the invention by providingthe feedback signal as a haptic or tactile signal.

The transmission of a haptic or tactile signal in conjunction with aselection performed in the gearbox to the clutch pedal unmistakablyinforms the driver that he can again engage a gear. Consequently, hefeels the signal at the point at which actuation is to be performed.This tactile signal is not burdensome for the driver, and it also doesnot represent a distraction for him, as is possible in the case ofacoustic or optical signals. The transmission of the hatpic signal isnot bound to a gear selector lever or gear shift lever any longer, sothat the servo-assisted gear selector can also be used in a simplemanner in conjunction with an electronic gear selector, without manualpreselection.

Realization is possible electrically in conjunction with, anelectromagnet, but also electropneumatically or electrohydraulically, inconjunction with a solenoid valve. The electromagnet can be connectedvia a short linkage to the clutch pedal, but it may also be arrangeddirectly in the plate of the clutch pedal. The intensity of the hapticor tactile signal can be adjusted in a simple manner via a potentiometerwith which the voltage is regulated. The arrangement of a signalgenerator in the form of an electromagnet in conjunction with a pressurepiston which acts on the pressure line between a transducerpiston-generator unit at the clutch pedal and a slave piston cylinderunit at the clutch is especially favorable. The pressure signalgenerated is transmitted via the transducer piston-cylinder unit and thelinkage to the clutch pedal and can be felt at the driver's foot. Thesignal may also be generated via pressurized media, in which case anelectropneumatic 3/2-way valve can release compressed air, aftershifting is completed from a pressurized medium source to a signalgenerator, which generates a pressure shock via a differential piston,and this pressure shock is again transmitted to the clutch pedal via thetransducer piston-cylinder unit and a linkage.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of my inventionwill become readily apparent from the following description, referencebeing made to the accompanying highly diagrammatic drawing in which:

FIG. 1 is a connection diagram of an electropneumatic circuit embodyingthe invention;

FIG. 2 is an enlarged sectional view which an electrical signalgenerator arranged in the clutch pedal;

FIG. 3 is a connection diagram of a servo-assisted actuating mechanismor a clutch with an electromagnet and a pressure piston as a signalgenerator; and

FIG. 4 is a diagram of a servo-assisted actuating mechanism for a clutchwith an electropneumatic valve and a differential piston unit as asignal generator.

SPECIFIC DESCRIPTION

The connection diagram for an electropneumatic gear selector of FIG. 1shows a vehicle gearbox 1 with a valve block 11 and three selectingcylinders 12, 13, and 14 for, e.g. three groups of gears. A pressurizedmedium, e.g. compressed air, is admitted into the valve block in theknown manner via a line 15. A gear selector 2 with a range selector 21,an accelerator pedal 3 with a load transducer 31, as well as an opticalgear display 4 are connected to an electronic control unit 5 viaelectrical lines 22, 32, and 42. An electronic tachograph 6 is alsoconnected via lines 61 and 62 to both an electrical pulse generator 16on the gearbox 1 and the electronic control unit 5, and a clutch pedal 7is connected via the release switch 71 to said valve block 11 via line72 and to control device 5 via line 73.

The connection to the vehicle's electrical supply system is designatedby reference numeral 65, and an engine brake switch is designated byreference numeral 45.

The electronic control unit 5 is switched to "gear selected" positionwith the electronic inductive transducer 17 via line 51, with the valveblock 11 via line 52, with the switch 18 for the neutral position vialine 53, and with the display switch 19 for "gear selected" via line 54.

Yet another signal generator 8 is arranged at the clutch pedal 7; thissignal generator 8 receives an electrical signal from the display switch19 on the gearbox 1 primarily via the electronic control unit 5 and line55 and transforms it into a haptic signal which is felt by the driver atthe clutch pedal 7 when the selection in the gearbox has been completed.A gear can be engaged only after this signal has been perceived. Thissignal replaces the information on completed selection in aservo-assisted gear selector, which can be felt via the shifting linkageon the gear shift lever in the case of an ordinary manual gear selectoror a system which informs the driver of completion of selection by,e.g., optical or acoustic signals in the case of servo-assisted gearselectors.

If said signal generator 8 is an electromagnet, as is shown in FIG. 1,the haptic signal is transmitted via the armature 81 to the clutch pedal7.

As is shown n FIG. 2. the electromagnet 80 may also be arranged directlyin the pedal plate 75, so that the armature 81 can transmit the hapticsignal directly or via a transmitting plate 76 to a surface area, e.g. arubber plate or a rubber profile 77, with which said pedal plate 65 iscovered. Because the driver keeps the clutch pedal actuated (clutchpressed down) in this state in which selection in the gearbox has notyet been made or, if the signal arrived it has just been made, he feelsthis signal in a simple manner without any optical or acoustic nuisance,and he can again release the clutch pedal 7 for engaging. It is alsopossible to arrange a potentiometer 82 in the electrical line 56 leadingto the electromagnet 80 for setting the voltage, because the intensityof the haptic signal can thus be regulated.

FIG. 3 shows the clutch pedal 70 in conjunction with a transducerpiston-cylinder unit 9, a line 91 for a pressurized medium, and a slavepiston-cylinder unit 95. As is apparent from FIG. 4, the piston of theslave piston-cylinder unit is mechanically connected to the clutchrelease mechanism 180 of clutch 190 and actuates said clutch. Losses ofpressurized medium are compensated for via a container 2 for pressurizedmedium, and a pressure piston 93 acting on the line 91 for thepressurized medium is actuated via an electromagnet 94 and acts as asignal generator for the haptic signal. The clutch is disengaged duringthe selection process in the gearbox 1 as a consequence of the clutchpedal 70 being actuated. The actuation takes place over the shortlinkage 74, the transducer piston-cylinder unit 9, and the pressurizedmedium, e.g. hydraulic oil in line 91, to the slave piston-cylinder unit95.

Once the desired gear has been engaged in the gearbox 1, the displayswitch 19 sends "gear selected" to the electronic control unit 5 vialine 54, and the electromagnet 94 is energized by the electronic controlunit via electrical line 57. A pressure signal, which is transmitted asa single shock or at intervals to the clutch pedal 70 via the transducerpiston-cylinder unit 9 and the linkage 74, is generated in line 91 viathe pressure piston 93. The driver feels the pressure signal at his footand can release the clutch pedal 70, because shifting in the gearbox hasbeen completed. FIG. 4 shows a possibility for generating the hapticsignal acting on clutch pedal 700 via a signal generator 10 inconjunction with an electropneumatic 3-part, 2-position valve 120,especially when the pressurized agent for actuating the clutch and thegears is air. As is described in connection with FIG. 3, the 3/2 valveis activated, like the electromagnet 94, after completion of theshifting in the gearbox 1. Pressurized medium is thus sent from a source110 of pressurized medium via the opened electrical 3/2 valve 120 to thesignal generator 10. The actual haptic signal in the pressure line 130is generated via a differential piston 101 and, as is described in FIG.3, it is transmitted via the transducer piston-cylinder unit 140 and thelinkage 150 to the clutch pedal 700. A pressure reducing valve 160 mayalso be provided to define the haptic signal. As is described inconnection with FIG. 3, line 130 is connected to the actuatingpiston-cylinder unit 170 for the clutch 190, and piston 171 is connectedto the clutch release mechanism 180.

I claim:
 1. A gear-selection assembly, comprising:a vehicle gearbox;servoassist means operatively connected with said gearbox for shiftinggears thereof; operator-controlled gear-selection means operativelyconnected to said servoassist means for selecting a gear into which saidgearbox is to be shifted; a clutch pedal depressable by an operator inresponse to actuation of said operator-controlled gear-selection meansto enable shifting of gears by said gear box; and means responsive to agearshift performed in said gearbox for generating a haptic signal andapplying said signal to said clutch pedal in a form tactilely sensed bysaid operator while said clutch pedal is depressed, to indicate thatsaid clutch pedal can be released to reengage gears following shiftingthereof.
 2. A gear-selection assembly, comprising:a vehicle gearbox;servoassist means operatively connected with said gearbox for shiftinggears thereof; operator-controlled gear-selection means operativelyconnected to said servoassist means for selecting a gear into which saidgearbox is to be shifted; a clutch pedal depressable by an operator inresponse to actuation of said operator-controlled gear-selection meansto enable shifting of gears by said gear box; and means including asignal generator arranged at or on said clutch pedal and responsive to agearshift performed in said gearbox for generating a haptic signal andapplying said signal to said clutch pedal in a form tactilely sensed bysaid operator while said clutch pedal is depressed, to indicate thatsaid clutch pedal can be released to reengage gears following shiftingthereof.
 3. The gear-selection assembly defined in claim 2 wherein saidsignal generator is an electrical signal generator.
 4. Thegear-selection assembly defined in claim 3 wherein said signal generatorincludes an electromagnet arranged in a plate of said clutch pedal, andan armature of the electromagnetic acting directly on a cover of theclutch plate.
 5. The gear-selection assembly defined in claim 3 whereinsaid signal generator includes an electromagnet arranged in a plate ofsaid clutch pedal, and an armature of the electromagnet acting on acover of the clutch plate via a transmission plate.
 6. Thegear-selection assembly defined in claim 3 wherein said signal generatorincludes an electromagnet and a potentiometer is connected in circuitwith said signal generator for regulating said haptic signal.
 7. Agear-selection assembly, comprising:a vehicle gearbox; servoassist meansoperatively connected with said gearbox for shifting gears thereof;operator-controlled gear-selection means operatively connected to saidservoassist means for selecting a gear into which said gearbox is to beshifted; a clutch pedal depressable by an operator in response toactuation of said operator-controlled gear-selection means to enableshifting of gears by said gear box; and means including a pressure shockgenerator responsive to a gearshift performed in said gearbox forgenerating a haptic signal in the form of a pressure shock and applyingsaid signal to said clutch pedal in a form tactilely sensed by saidoperator while said clutch pedal is depressed, to indicate that saidclutch pedal can be released to reengage gears following shiftingthereof.
 8. The gear-selection assembly defined in claim 7 wherein saidmeans for generating a haptic signal includes:a transducerpiston-cylinder unit at said clutch pedal and coupled thereto; a slavepiston-cylinder unit at a clutch operated by said pedal; a pressure lineconnecting said units; a pressure piston connected to said pressure lineand actuatable to generate a pressure shock therein; and means foroperating said pressure piston to produce said pressure shock wherebysaid pressure shock is transmitted as said haptic signal to said clutchpedal.
 9. The gear-selection assembly defined in claim 7 wherein saidmeans for generating a haptic signal includes:a transducerpiston-cylinder unit at said clutch pedal and coupled thereto; a slavepiston-cylinder unit at a clutch operated by said pedal; a pressure lineconnecting said units; a pressure piston connected to said pressure lineand actuatable to generate a pressure shock therein; and means includingan electropneumatic directional control valve for operating saidpressure piston to produce said pressure shock whereby said pressureshock is transmitted as said haptic signal to said clutch pedal.
 10. Thegear-selection assembly defined in claim 9 further comprising anadjustable pressure reducing valve between a source of pressurizedmedium and said electropneumatic directional control valve.